从java数组中获取五个随机元素

Question

我已经在这个项目上工作了几天，我能够完成大部分工作，但我一直在努力从我的阵列中取出五个不同的项目。我可以选择五次相同的项目。

我的代码如下所示：

public class CardGuessingGame {

    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {

        String[] myCards = new String[]{"two", "three", "four", "five", "six", "seven", "eight", "nine", "ten", "jack", "queen", "king", "ace"}; // Array for cards

        Random rand = new Random(); //random construction
        rand.nextInt(13); // Sets rand to 0-12 int
        //int randomNums = rand.nextInt(13); // sets randNums from 0-12
        int randomNums = rand.nextInt(myCards.length); //Randomizes "randomNums to the length of the array"
        String cardInHand = myCards[(int)randomNums];

        for (randomNums=0; randomNums < 5; randomNums++) {

            System.out.println(cardInHand);
        }

        System.out.print("Guess the card in my hand: "); // Prints to user asking for guess

        Scanner answer = new Scanner(System.in); // gets user input
        String s = answer.nextLine(); //stores user input inside variable s

        if(s.equals(cardInHand)) {

            System.out.println("I do have that card in hand");
        } else {

            System.out.println("I do not have that card in hand!");
        }

        System.out.print("These were the cards I had in hand: ");
        System.out.println(cardInHand);
    }
}

这是输出

run:
four
four
four
four
four
Guess the card in my hand: four
I do have that card in hand
These were the cards I had in hand: four

我现在拥有的东西可以工作，但不正确。

Answer 1

1. 我认为您对 rand.nextInt(13) 的作用存在误解。在这里，您正确地创建了 random 对象，但是第二行，您认为它将 rand 设置为 0-12，而实际上它只是调用一个方法来返回一个从 0-12 的随机整数，并且完全没有做任何事情。

   Random rand = new Random(); //random construction
   rand.nextInt(13); // Sets rand to 0-12 int
   

2. 一个。您将变量 randomNums 设置为某个随机值，我不知道为什么，当您在 for 循环中将其重置为零之前，然后再进行任何可能的使用。

   b.您存储卡片的一般方法是不正确的，因为您应该创建一个新的 ArrayList 来存储 5 张卡片，但实际上，您只生成了一张卡片并打印了 5 次

   int randomNums = rand.nextInt(myCards.length);
   String cardInHand = myCards[(int)randomNums];
   for (randomNums=0; randomNums < 5; randomNums++) {
       System.out.println(cardInHand);
   }
   

这就是您的代码的更简洁、更合乎逻辑的版本应该是什么样子。

String[] myCards = {"two", "three", "four", "five", "six", "seven", "eight", "nine", "ten", "jack", "queen", "king", "ace"};
Random rand = new Random();
Scanner scan = new Scanner(System.in);
int cardIndex = rand.nextInt(myCards.length);
ArrayList<String> playerHand = new ArrayList<>();
for (int i = 0; i < 5; i++) {
    while (playerHand.contains(myCards[cardIndex]))
        cardIndex = rand.nextInt(myCards.length);
    playerHand.add(myCards[cardIndex]);
}
System.out.print("Guess the card in my hand: ");
if(playerHand.contains(scan.nextLine()))
    System.out.println("I do have that card in hand");
else
    System.out.println("I do not have that card in hand!");
System.out.print("These were the cards I had in hand: ");
System.out.println(playerHand);

Answer 2

我编写了新代码来加深您在阅读源代码时的歧义。因此，我在某些行中添加了注释以清楚地理解。

public class CardGuessingGame  {

    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {


        //list of cards
        List<String> myCards = Arrays.asList("two", "three", "four", "five", "six", "seven", "eight", "nine", "ten", "jack", "queen", "king", "ace");
        //shuffle cards
        Collections.shuffle(myCards);

        //get first 5 elements from shuffled list
        HashSet<String> myHand = new HashSet<>();
        for (int i = 0; i < 5; i++) {
            myHand.add(myCards.get(i));
            System.out.println(myCards.get(i));
        }

        System.out.print("Guess the card in my hand: "); // Prints to user asking for guess

        Scanner answer = new Scanner(System.in); // gets user input
        String s = answer.nextLine(); //stores user input inside variable s

        //if set contains , you found the card
        if (myHand.contains(s)) {
            System.out.println("I have that card in my hand");
        } else {
            System.out.println("I do not have that card in hand!");
        }

        System.out.print("These are the cards which is in my hand: ");
        //write all cards in my hand with sepearete comma
        System.out.println(String.join(",", myHand));
    }
}

Answer 3

这是一个有效的代码，只需要唯一的卡片。首先，您应该知道哪些变量是数组，哪些不是。

对rand.nextInt(13); 的调用不会将 Random 实例设置为生成 1 到 13 之间的随机数，但实际上会生成一个。

你的随机数生成应该放在循环中。手头的卡片需要包含多个值，因此应使用数组。

import java.util.Arrays;
import java.util.Collections;
import java.util.LinkedList;
import java.util.List;
import java.util.Scanner;

public class CardGuessingGame {

    /**
     * @param args
     *            the command line arguments
     */
    public static void main(String[] args) {

        String[] myCards = new String[] { "two", "three", "four", "five", "six", "seven", "eight", "nine", "ten",
                "jack", "queen", "king", "ace" }; // Array for cards

        //Random rand = new Random(); // random construction
        //rand.nextInt(13); // Sets rand to 0-12 int
        // int randomNums = rand.nextInt(13); // sets randNums from 0-12

        String[] cardsInHand = new String[5];

        List<String> cards = new LinkedList<>(Arrays.asList(myCards));
        Collections.shuffle(cards);

        for (int i = 0; i < 5; i++) {
            //This will not give you unique cards!
            //int randomNums = rand.nextInt(myCards.length); // Randomizes "randomNums to the length of the array"
            cardsInHand[i] = cards.remove(0);
        }

        System.out.println(Arrays.toString(cardsInHand));

        System.out.print("Guess the card in my hand: "); // Prints to user asking for guess

        Scanner answer = new Scanner(System.in); // gets user input
        String s = answer.nextLine(); // stores user input inside variable s


        //Some kind of contains method. You can traverse the array use a list or do however you like
        Arrays.sort(cardsInHand);

        if (Arrays.binarySearch(cardsInHand,s) >= 0) {

            System.out.println("I do have that card in hand");
        } else {

            System.out.println("I do not have that card in hand!");
        }

        //Close the stream
        answer.close();

        System.out.print("These were the cards I had in hand: ");
        System.out.println(Arrays.toString(cardsInHand));

    }
}

Answer 4

首先，我将尝试解释你哪里出错了，并给你和工作代码的例子。

我假设您应该只为此使用数组，并且您不能重复数字。

第一

您将cardInHand 设置为myCards[(int)randomNums]。然后循环5 次并将cardInHand 打印到控制台。您永远不会将卡片设置为其他任何东西。

第二

即使您将cardInHand 设置为其他值，您现在也丢失了之前的卡信息。您缺少的是另一个用于保存卡信息的数组。这可以通过使用循环来完成。

for(int i = 0; i < 5; i++)
{
    cardInHand = myCards[rand.nextInt(myCards.length)];
    cardsInHand[i] = cardInHand;
}

这样就实现了将卡片保存到数组中以备后用。

这是解决您的问题的有效代码。

String[] myCards = new String[]{"one", "two", "three", "four", "five", "six", "seven", "eight", "nine", "jack", "queen", "king", "ace"};
Random rand = new Random();
String[] cardsInHand = new String[5];
int[] usedNums = new int[5];

for(int i = 0; i < 5; i++)
{
    usedNums[i] = -1;
}

for(int i = 0; i < 5; i++)
{
    int randNum = rand.nextInt(myCards.length);
    boolean contains = false;
    do
    {
        for(int j = 0; j < 5; j++)
        {
            if(usedNums[j] != randNum)
            {
                contains = false;
                continue;
            }
            contains = true;
            randNum = rand.nextInt(myCards.length);
        }
    }
    while(contains);
    cardsInHand[i] = myCards[randNum];
    usedNums[i] = randNum;
}

Scanner answer = new Scanner(System.in);
String s = answer.nextLine();

boolean hasCard = false;

for(int i = 0; i < 5; i++)
{
    if(cardsInHand[i].equals(s)
    {
        hasCard = true;
        break;
    }
}

if(hasCard)
{
    System.out.println("Has card");
}
else
{
    System.out.println("Not has card");
}

System.out.println("Cards in hand:");
for(int i = 0; i < 5; i++)
{
    System.out.println(cardsInHand[i]);
}

如果您可以使用重叠数字，则删除对 usedNums 和 do..while 循环的引用。